The present invention relates generally to single use syringes having safety features and more specifically to a single use syringe having a plunger locking mechanism and safety shield.
In the United States and throughout the world, the multiple use of hypodermic syringe products that are intended for single use only, is instrumental in drug abuse and more particularly in the transfer of diseases. Intravenous drug users who routinely share and reuse syringes are a high-risk group with respect to the bloodborne pathogens including HIV and AIDS. Also the effects of multiple use are a major concern in under-developed countries where repeated use of syringe products may be responsible for the spread of many diseases. Reuse of single use hypodermic syringe assemblies is instrumental in the spread of drug abuse even in the absence of infection or disease.
Many attempts have been made to remedy this problem. Some of these attempts have required a specific act to destroy the syringe after use either by using a destructive device or providing a syringe assembly with frangible zones so that the syringe could be rendered inoperable by application of force. Other attempts have involved the inclusion of structure which would allow the destruction or defeating of the syringe function through a conscious act by the syringe user. Although many of these devices work quite well, they do require the specific intent of the user followed by the actual act to destroy or render the syringe inoperable.
Furthermore, in the medical arts, a syringe assembly typically includes a sharp pointed needle for administering fluids to patients either directly or into intravenous apparatus, and in various blood drawing applications either with syringes or with specialized holders for filling evacuated tubes. Since needles are widely used for medical procedures, many people can be exposed to needles in the routine course of their work.
Accidental needle sticks from used hypodermic needles can transmit disease. Accordingly, various types of needle shields such as hinged needle shields, have been designed to reduce the possibility of accidental sticks.
Various means have been provided for locking a hinged needle shield in the closed (needle protecting) position. Needles are available in a number of gauges and lengths so that they can be used for different purposes. Where a needle shield having a deflectable locking member is used to entrap a needle, it is important that the needle displace the locking member or members as it enters the needle shield cavity. It is also important that, since the needle is entrapped by the deflectable locking member or members, it cannot easily be displaced from the cavity. A relatively large diameter needle can more easily displace a deflectable locking member than a small diameter needle, both entering the needle shield cavity and exiting the cavity. As a needle shield should preferably be usable to protect needles of various sizes, the deflectable locking member or members should be designed such that it is sufficiently flexible to allow even a relatively small diameter needle to deflect it as it enters the needle shield cavity, but provides sufficient resistance to prevent the needle from being re-exposed through the opening of the cavity.